The present invention relates generally to the field of containers for the transportation of general cargo, and in particular, to containers which may be collapsed into a compact configuration for storage or return to a point of origin.
Shipping containers in which the walls fold to form a collapsed configuration are well known. Such containers have the advantages of allowing a compact folded configuration which facilitates storage and shipment. Quite commonly, a manufacturer ships parts to a distant point of assembly from which empty containers must be returned to the manufacturer. It is of course highly inefficient to ship empty containers; therefore, many attempts have been made to develop a collapsible container which demonstrates efficiency, durability, ease of use, minimum collapsed configuration, flexibility of use, and strength.
One of the problems associated with the use of collapsible containers is ensuring that the unfolded configuration has the requisite degree of strength. Various patents disclose the use of corner posts to tie together the side panels in a collapsible shipping container. U.S. Pat. No. 3,266,656 issued to Kridle on Aug. 16, 1966 for "Demountable Shipping Case" discloses a collapsible shipping container with a base having a flange around its outside edge, four rectangular side panels, four corner posts each having a pair of channels to receive the vertical edges of the side panels, and a cover. The side panels of Kridle, however, are not hinged and the corner posts do not disclose the use of pins to tie the side panels together.
U.S. Pat. No. 4,174,045 issued to Heller on Nov. 13, 1979 for "Loading Platform" does, however, disclose corner posts which have a plate at the top with a slot to receive extensions formed in the top edges of the side panels.
Another shipping container disclosing corner connectors is U.S. Pat. No. 5,236,099 issued to Fties et al. on Aug. 17, 1993 for "Plastic Knock Down Bin-Pallet for Loading, Transporting and Storing Fruits, Vegetables, Fish or Other Foods." Fties et al. disclose corner connectors which have a pair of channels for interlocking with the side panels of a collapsible container.
U.S. Pat. No. 3,401,814 issued to Chiswell on Sep. 17, 1968 for "Collapsible Shipping Container" discloses a container having a base and four corner posts, four detachable side panels and a roof section. The same type of corner posts are disclosed in U.S. Pat. No. 4,050,604 issued to Flanders on Sep. 27, 1977 for "Disassembleable, Reusable Container." In both of these patents, the corner posts are simple angle pieces which do not provide channels to receive the edges of the side panels.
Many designs of collapsible shipping containers employ the concept of folding the side walls about hinges. Some of the problems associated with the use of hinges include the durability of the container and its strength, both in the collapsed and the unfolded configuration. One particular problem is to avoid the loading of the hinges which can promote premature failure in the fully unfolded configuration and which may limit the ability of the folded or collapsed configuration to be stacked for efficient shipment. The following are examples of patents for collapsible shipping containers in which some or all of the walls are hinged to the bottom portion. U.S. Pat. No. 4,858,779 issued to Zimmerlund on Aug. 22, 1989 for "Container" is a somewhat complicated arrangement for folding the sides together to form a compact package. Zimmerlund does, however, recognize the problem of arranging the hinges so that the panels bear on one another and not on the hinge structure itself.
U.S. Pat. No. 5,253,763 issued to Kirkley on Oct. 19, 1993 for "Collapsible Container" discloses a container in which two of the side walls are hinged and two of the side walls are removable for stacking onto the folded hinged sides. Kirkly does not disclose the use of corner posts and the appropriate stacked configuration is obtained by folding the side panels about central hinges.
A final example of a shipping container in which the sides are hinged is U.S. Pat. No. 3,040,925 issued to Mills on Jun. 26, 1962 for "General Cargo Shipping Container." Mills recognizes the desirability of being able to open a side of a shipping container for easy loading and unloading.